The relationship between student study time allocation and examination performance is little understood. We model the allocation of student time into formal study (lectures and classes) and self study and its relationship to university examination scores using a stochastic frontier production function. This case study uses unique time budget data and detailed personal records from one university in Spain. The results suggest that, within the formal system of teaching in Spain, both formal study and self study are significant determinants of exam scores but that the former may be up to four times more important than the latter. We also find that self study time may be insignificant if ability bias is corrected for.